feat(env): Add script to set PKG_CONFIG_PATH for DB clients

Provide a script to check and set PKG_CONFIG_PATH for libpq and
mysql-client on macOS via Homebrew. This helps prevent build errors
for database libraries and guides users to install missing dependencies.

Author: jiacai2050

env.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+# This script is primarily intended for macOS users using Homebrew.
+# It sets up PKG_CONFIG_PATH for database client libraries.
+
+if ! command -v brew &> /dev/null; then
+    echo "Error: Homebrew (brew) is not installed." >&2
+    return 1 2>/dev/null || exit 1
+fi
+
+if ! brew list libpq &>/dev/null; then
+    echo "Error: libpq is not installed. Please run 'make install-deps' to install it." >&2
+    return 1 2>/dev/null || exit 1
+fi
+
+if ! brew list mysql-client &>/dev/null; then
+    echo "Error: mysql-client is not installed. Please run 'make install-deps' to install it." >&2
+    return 1 2>/dev/null || exit 1
+fi
+
+PREFIX=$(brew --prefix)
+export PKG_CONFIG_PATH="${PREFIX}/opt/libpq/lib/pkgconfig:${PREFIX}/opt/mysql-client/lib/pkgconfig"